bug#44284: 27.1; with some Unicode font, scrolling upward with the mouse wheel actually scrolls downward when the cursor needs repositioning

[Eli Zaretskii]

> Date: Sun, 1 Nov 2020 01:28:03 +0100
> From: Vincent Lefevre <vincent@vinc17.net>
> Cc: 44284@debbugs.gnu.org
> 
> On 2020-11-01 01:24:30 +0100, Vincent Lefevre wrote:
> [...]
> > where row->height is increased to 14, hence the issue with the first
> > line. One successively gets
> > 
> >   it->current_y = 0
> >   it->current_y = 14
> >   it->current_y = 27
> > 
> > adding 13 each time for the following lines.
> 
> About this, this is in function display_line
> 
>   it->current_y += row->height;

Yes, this is how the display engine tracks the Y coordinate of the
screen line it is laying out.